1. Field of the Invention
The presently disclosed subject matter relates to an autofocus system, and more particularly to an autofocus system having a function of enabling a predetermined subject to be automatically tracked by an AF frame (AF area) representing a range of a subject focused by autofocus (AF).
2. Description of the Related Art
Conventionally, in an autofocus (AF) system for automatically setting the focus of a camera, it is necessary to instruct the camera where the focus of the camera is to be set. At this time, in a common camera, and the like, the focusing position is fixed at the center of a shooting range. Thus, the focus of the camera is set to, for example, a person located at the center of the shooting range.
However, in such a case where a moving subject is shot (photographed), it is inconvenient for shooting if the focusing position is fixed in this way. Thus, an autofocus system is known, in which, for example, when a scene of a quickly moving subject in a sporting event, and the like, is shot by a television camera and the like, the AF area (AF frame) of the television camera is configured to automatically track the subject in order that the focus of the camera is set to the subject (see, for example, Japanese Patent Application Laid-Open No. 2006-267221). Note that in this specification, similarly to the AF area, the AF frame representing the contour of the range of the AF area is mainly used as a term which means the range of a subject to be focused.
Further, a digital camera is known, which detects an image representing a human face from an shot image, so as to automatically set the focus of the camera to the face set as the subject, or so as to automatically change the zoom magnification to enlarge the area representing the face in the detected image (see, for example, Japanese Patent Application Laid-Open No. 2004-320286).